DARBY, Pa. — A doctor told police that a patient fatally shot a caseworker at their hospital complex before the doctor pulled out his own gun and exchanged fire with him and wounded him, a prosecutor said Thursday night.

Dr. Lee Silverman, a psychiatrist, was grazed in the temple during the gunfight in his office with patient Richard Plotts, according to Delaware District Attorney Jack Whelan.

Whelan identified the caseworker killed Thursday afternoon at Mercy Fitzgerald Hospital as Theresa Hunt, 53. Hunt, who was from Philadelphia, had accompanied Plotts to an appointment with Silverman at a psychiatric crisis center next to the hospital in Darby, just southwest of Philadelphia, authorities said.

"When the caseworker was shot, (Silverman) crouched down behind the desk to avoid him being shot," Whelan said. "He was able to reach for his weapon, and realizing it was a life or death situation, was able to engage the defendant in the exchange of gunfire."

A struggle ensued and spilled out into the hallway, Whelan said. Another doctor and a caseworker jumped in to help Silverman and secure Plotts' weapon, he said.

The motive for the shooting remained unclear late Thursday, although Whelan said Plotts, of Upper Darby, might have had issues with the doctor over his treatment plan. However, it's unclear if that's why Silverman was armed, apparently against hospital policy.

"We do believe that there were some issues between the doctor and the patient, but whether or not he actually feared him is unclear," the prosecutor said. "From all accounts, (he) would have acted in self-defense."

Whelan said that Plotts, 49, was still in surgery Thursday evening at the Hospital of the University of Pennsylvania, while Silverman had been treated and released. Telephone calls to the doctor's home went unanswered.

Plotts doesn't have a listed home phone number. Court records in Delaware County show a man of the same name and age with a lengthy criminal record, but Whelan was uncertain if they were the same person.

The hospital has a policy barring anyone except on-duty law enforcement officers from carrying weapons on its campus, a spokeswoman for the Mercy Health System said.

But Yeadon Police Chief Donald Molineux said that "without a doubt, I believe the doctor saved lives."

"Without that firearm, this guy (the patient) could have went out in the hallway and just walked down the offices until he ran out of ammunition," the chief said.

Two guns were recovered from the scene, Whelan said.

Staff members had heard loud arguing inside Silverman's office during the appointment. They opened the door and noticed the patient had a gun pointed at the doctor, so they quietly closed the door and dialed 911, Whelan said. Gunshots were heard a short time later, just before 2:30 p.m.

Plotts, severely wounded from several shots, emerged from the office, and another doctor and a caseworker helped wrestle him to the floor of the hallway and grabbed his weapon, Whelan said.

"They acted vigilantly. They acted bravely," he said.

The exchange of gunfire occurred on the third floor of the Wellness Center at Mercy Fitzgerald, a 204-bed community teaching hospital. Authorities said there are no surveillance cameras in the doctor's office or the waiting area outside. They also said the center had no metal detectors.

Patients waiting in the first-floor lobby reported a tense scene when police arrived and ordered everyone out. Most of the patients were elderly.

"I dozed off, and I heard the cop shouting, 'Come on, come on, get out!'" said Millicent Russell, of Lansdowne, who was waiting for a 3 p.m. appointment. "There were people with walkers and canes and stuff. All these cops were outside running here and there with these guns."